Surgical techniques to correct or address spinal problems are turning more and more to non-fusion technologies. One type technology involves spinous process stabilization. Spinous process stabilization is further explained in U.S. patent application Ser. No. 11/128,960 filed, May 12, 2005, titled SPINAL STABILIZATION, which application is incorporated herein as if set out in full. Another similar technology comprises using conventional pedicle screws.
One conventional pedicle based stabilization system includes a pedicle screw platform threaded into at least a superior and inferior pedicle. Stabilizing cords a placed and spacers inserted between sets of pedicle screws. Once everything is placed, the cords are tightened.
Conventional pedicle based systems, such as the one explained above, provide adequate support, however, any flex of the system is abruptly stopped by either the cord or the spacer. Even if the spacer provides for some flex, the cord provides an abrupt stop in the opposite direction.
Some pedicle screw stabilization devices provide tracks to allow some movement. For example, the spacer may have elongated slots or tracks on the superior and/or inferior end the spacer to move relative to the pedicle screw, which allows for some relative movement between the superior and inferior vertebrae. The track provides more flex than the spacer/cord systems, but provides abrupt stops in both directions.
However, one problem with a pedicles screw based systems is over time the pedicle screws loosen and the stabilization device fails over time. The screws loosen, in part, because the motion inhibits the screw from fusing to the bone.
Thus, it would be desirous to develop a pedicle screw based spinal stabilization apparatus that provide a mechanism to prompt fusion.